. >> the lead author of the latest u.n. report is kevin schaffer. he gave a briefing in doha, qatar, on the sidelines of the u.n. conference on climate change. the authors say permafrost contains huge amounts of carbon in the form of frozen organic matter. their estimate is 1,700 gigatons, twice the amount of carbon currently in the atmosphere. permafrost covers a quarter of the northern hemisphere including large parts of siberia and canada. the report says it could release as much as 135 gigatons of co2 by the end of the century. it warns of radical changes in ecosystems and costly damage to human infrastructure as well. >> permafrost tends to be hard and very durable, but when it thaws the ice turns to water and permafrost gets soft and infrastructure built on top of it can collapse. >> the report comes as delegates from around the world negotiate ways to reduce greenhouse gases at the conference. the scientists warn emissions from permafrost could start in the next few decades. >>> youngsters are at the climate talks to warn about the impact of global warming around the planet.